import java.util.Scanner;

/**
 * Created by forcht on 2018/4/25.
 */
public class Main {

    public static void main(String[] args) {
        Scanner scanner=new Scanner(System.in);
        String s=scanner.nextLine();
        String[] split = s.split("/");
        String[] str = split[split.length - 1].split("\\.");
        if(str.length>1&&str[str.length-1].length()>0){
            System.out.println(str[str.length-1]);
        }else {
            System.out.println(null+"");
        }
    }
}
